The purpose of this R13 proposal is to seek partial support for the 3rd International Thumb Osteoarthritis Workshop (ITOW 2018), which will be held on November 8-10, 2018, at the Stanford University School of Medicine. The workshop is focused on thumb carpometacarpal (CMC) osteoarthritis (OA), and will bring together clinicians and basic researchers from multiple disciplines involved in advancing the treatment of thumb CMC OA. The workshop will provide a unique, focused forum for the cross-discipline exchange of information regarding the etiology, pathogenesis, treatment and clinical outcome of the disease. Thumb CMC OA is a widespread and disabling disease that affects 21% of people over the age of 40, and two-thirds of women over the age of 55. Pain, weakness, and loss of dexterity of the thumb lead to disabling impairment in hand and upper extremity function. Various aspects of CMC OA may be covered at other specialty meetings (such as the American Society of Biomechanics [ASB], the Orthopaedic Research Society [ORS], the Osteoarthritis Research Society International [OARSI], and the American Society for Surgery of the Hand [ASSH]), but our workshops are currently the only focused, integrative meetings designed to address the disease specifically. As with our previous meetings, the 3rd ITOW will include presentations on the current state of knowledge, but also on innovative research that has the potential to influence treatment and clinical outcomes. The workshop will include three content areas: attendee podium presentations, keynote presentations, and a consensus development session. Cross-discipline communication and the stimulation of collaboration will emanate from the single-session format of the meeting program, the open panel discussions, and engaging social events, which will give the attendees additional opportunities to meet. The target audience includes basic scientists and clinicians who work on all aspects of CMC OA, including anatomists, biomechanists, cartilage biologists, neuroscientists, hand surgeons and rheumatologists. Special emphasis will be placed on the inclusion and mentoring of students and early-career investigators.